Conventionally, in many cases, a liquid crystal driver IC chip for driving a liquid crystal panel has been installed in the liquid crystal panel as a tape carrier package, which is one of the packages for a semiconductor device. Such a liquid crystal driver IC is installed, for example, in a liquid crystal panel module shown in FIG. 22.
As shown in FIG. 22, a liquid crystal panel 70 is provided with a plurality of tape carrier packages 72, each having a liquid crystal driver IC chip 71. Each tape carrier package 72 includes outer leads (not shown) connected to output terminals and the liquid crystal driver IC chip 71 respectively. The liquid crystal driver IC chip IC 71 is connected with the liquid crystal panel 70 via the outer leads for the output terminals and is connected with a flexible substrate 73 via the outer leads for the input terminals. A signal is transmitted and power is supplied to each of the liquid crystal driver IC chips 71 via wires disposed on the flexible substrate 73.
In recent years, because of a growing need for more compact and lightweight products in the marketplace, it has been necessary to develop a smaller version of a semiconductor device disposed in a liquid crystal panel. In order to meet such a demand, Japanese Unexamined Patent Publication No. 3684/1994(Tokukaihei 6-3684, published on Jan. 14, 1994) discloses a liquid crystal driver IC tape carrier package. FIG. 23 shows a construction of the liquid crystal driver IC tape carrier package disclosed in the above publication.
The above-mentioned liquid crystal driver IC tape carrier package is provided with a liquid crystal driver IC chip 117 at the center, input/output signal terminals 111 and 112 which are bilaterally symmetrical, and a liquid crystal drive output terminal 115 at the center. This construction supplies electricity and transmits various signals (for example, controlling signals such as a clock, a start signal, and a synchronizing signal) by using wires in the liquid crystal driver IC chip 117. With this arrangement, it is not necessary to provide a flexible substrate for supplying power and transmitting various signals.
Generally, it has been required that such a liquid crystal panel module be still more compact and lightweight at lower cost.
However, in the construction which supplies power and transmits various signals by using the wires of the liquid crystal driver IC chip 117, when a number of tape carrier packages are connected, a voltage drop may occur especially on power supplying wires due to an increase in the number of connected tape carrier packages, resulting in degradation in display quality of the liquid crystal panel.
Here, the power supplying wires, which use the wires of the liquid crystal driver IC chip 117, are, for example, those connected to liquid crystal driving power source.
Voltage from the liquid crystal driving power source causes a voltage drop due to resistance on the wires of the liquid crystal driver IC chip 117, and proper driving conditions are not satisfied, resulting in degradation in display quality of the liquid crystal panel. Further, voltage from a logic driving power source is also supplied by using the wires inside the chip; thus, again, a voltage drop may cause an adverse effect on a logic operation. Generally, a liquid crystal panel is normally driven by connecting a number of liquid crystal driver IC chips to the liquid crystal panel, and the greater is the number of LCD IC chips connected, the more serious is the described problem of voltage drop.